When Carmen is packing and speaking to Julia, she puts the same red leather portfolio in her bag twice.
When Bridget is talking to Greta during the thunderstorm, a section of her hair on her right side is pulled behind her ear and not pulled behind her ear many times.
When Lena is in bed in Greece, the lighting on her face changes inconsistently between shots. From some camera angles, the light is coming from her left; from others, it is coming from her right; in at least one, there is light on both sides.
When Lena is talking to Kostos at the restaurant, we see a man in a sweatshirt passing behind her. She looks in the direction of her friends. After the cut, this same man is in the upper background. Then after another cut he is past them.
The glasses Tibby and Brian are holding change color. At first, Brian is holding a light blue one and Tibby is holding a dark blue one. Brian puts the dark blue one on the floor and the light one is on the table (supposedly put there by Tibby).
In the soccer match at Brown University, one of Bridge's teammates has blue Adidas soccer cleats on. Brown University soccer players would only wear black or white soccer cleats.
In rehearsals, actors are shown holding scripts from Samuel French. The Winter's Tale is a public domain play and not carried by Samuel French.
When Bridget in Turkey, the Turkish people are shown like Arabian people. In reality, Turkey is a very modern country and Turkish people are quite modern as well. They aren't like people in the movie.
Tibby, Bridget and Carmen all go to Greece to help Lena try and find the pants. It takes at least two weeks to get a passport, and there is no evidence that Carmen or Tibby ever had one, so they could not come to Greece so quickly.
When Lena is at the funeral in the beginning of the movie, for someone of the Greek Orthodox faith, she makes the correct sign of the cross. The Greek Orthodox Church crosses itself from right to left rather then Roman Catholic left to right.
Lena's eye color changes multiple times between scenes, from blue to dark brown.
When Bridget finds the letters from Greta in her dad's basement that her father had hidden from her, there is no USPS cancellation stamp printed over any of the postage stamps. This would indicate the letters were intercepted before they were mailed. Since Greta lives in Alabama, this doesn't seem possible.